Patent GB-537957-A (GB)
Title: Improvements in or relating to the production or treatment of articles in gel form
IPC: B29C63/16
Filed: 1939-12-11
Abstract: 537,957. Cellulose derivative and synthetic resin compositions, films &c. ; ornamenting. BRITISH UNITED SHOE MACHINERY CO., Ltd. (United Shoe Machinery Corporation). Dec. 11, 1939, No. 31915. [Classes 2 (ii) and 2 (iii)] [Also in Groups V and XV] A composition comprising a linear polymer or a cellulose derivative and a low boiling organic liquid which is a solvent at elevated temperature but a non-solvent at a lower temperature is heated to form a sol, shaped into the desired form, and cooled so as to form a coherent lyogel, the proportions of the ingredients of the composition being such that get formation is accompanied by a small amount of syneresis. There may be used cellulose mixed esters or complex polymerization compounds, e.g. polymers obtained by conjoint polymerization of vinyl chloride and vinyl acetate, or polymers in which replaceable groups such as ester groups have been substituted in part by other groups, e.g. a polyvinyl acetate in which some of the acetate groups have been replaced by hydroxyl groups. When the solvent is allowed to evaporate the gels shrink considerably. The compositions may be used in the production of films or filaments and particularly in the production of thin coverings for articles such as shoe heels, or in the production of bottle caps, filter-membranes, or seamless packages Examples describe the production of compositions comprising cellulose aceto-propionate with mixtures of benzene and methanol or chloroform and methanol as solvent and similar compositions comprising cellulose acetobutyrate. Other examples describe compositions comprising co-polymers from vinyl chloride and vinyl acetate with chloroform or chloroform and benzene as solvent, and compositions comprising co-polymers from vinyl alcohol and vinyl acetate with a mixture of methanol and water as solvent. For obtaining a cover for an article such as a shoe-heel, the composition is cooled from the liquid state until it sets to a lyogel with syneresis. The wet gel is broken up and placed in hopper 9 of an injection moulding machine (Fig. 2). Plunger 15 forces lyogel into the heating chamber 17 with heating-jacket 19. The gel is converted into a sol and forced into a mould consisting of cavity-member 27 and die-member 29, both members being provided with cooling devices. A bag-shaped lyogel cover-blank 111 (Fig. 4) is obtained. It is removed from the mould, and a shoe heel, provided with adhesive which can be activated by solvent retained in the blank, is placed within the blank. The mouth of the blank is gathered about suction nozzle 113 (Fig. 6) and suction is applied through pipe 115 while the blank is heated. This causes the blank to shrink on to the heel 100 to form a tough flexible film-like covering. If desired the blank may be caused to shrink on to the heel by merely allowing it to stand at room temperature. Where the heel has a concave breast-portion, it is necessary to heat the heel and the blank and then press the blank into contact with the concave portion. The heel with the blank shrunk on its back and sides may be placed in container 123 (Fig. 9) which is made of flexible rubber. Hot water under pressure is forced into receptacle 119 to distort the rubber container 123 and cause it to press the blank 111 against heel 100, the heat serving also to soften the adhesive. Before inserting the heel in the lyogel blank, a disc 131 (Fig. 10) may be placed in the mouth of the blank and the solvent may be allowed to evaporate. The dry shrunken blank is then heated and expanded by forcing heated fluid into it. It is then quickly cooled and set in its expanded condition. The disc 131 is removed and the heel is placed in the blank which is then caused to shrink upon the heel, e.g. by heating and suction. Specifications 528,107 and 528,375 are referred to.